An apparatus for inflating an inflatable vehicle occupant restraint, such as an air bag, is disclosed in U.S. Pat. No. 5,131,680 (the '680 patent). The apparatus disclosed in the '680 patent includes a container which stores gas for inflating the vehicle occupant restraint. The apparatus further includes a body of pyrotechnic material and an igniter assembly for igniting the body of pyrotechnic material. The igniter assembly includes an ignition material which rapidly burns at a relatively high temperature to generate heat and flame. The heat and flame generated by the ignition material ignite the body of pyrotechnic material. As the body of pyrotechnic material burns, hot combustion products emitted by the body of pyrotechnic material pressurize and supplement the stored gas.
The apparatus disclosed in the '680 patent also includes an actuator assembly which operates in response to vehicle deceleration indicative of a collision. The actuator assembly operates to actuate the igniter assembly, and also to rupture a burst disk to release a flow of gas from the container. The actuator assembly includes an ignition material which, when ignited, generates pressure against the head of a piston to move the piston. The moving piston ruptures the burst disk and strikes the igniter assembly to ignite the ignition material in the igniter assembly. The ignition material in the igniter assembly then ignites the body of pyrotechnic material within the container.